In the Long Term Evolution (LTE) and earlier wireless communication systems, there is only one carrier with a bandwidth up to 20 MHz in a cell as illustrated in FIG. 1. In the Long Term Evolution-Advanced (LTE-A) system, there are required peak data rates of the system, up to 1 Gbps in the downlink and 500 Mbps in the uplink, as improved significantly compared to the LTE system. The required peak data rates can not be available with only one carrier with a bandwidth up to 20 MHz. Thus the technology of Carrier Aggregation (CA) has been introduced to the LTE-A system, where a plurality of contiguous or non-contiguous carriers served by the same evolved Node B (eNB) are aggregated together to serve a User Equipment (UE) concurrently as illustrated in FIG. 2. These carriers aggregated together are referred to as Component Carriers (CCs). Each cell can correspond to one component carrier, and cells (component carriers) served by different eNBs can not be aggregated. In order to ensure backward compatibility with a UE in the LTE system, there is a bandwidth of no more than 20 MHz for each of the carriers.
One of the component carriers aggregated for the UE is defined as a Primary Component Carrier (PCC) including a downlink PCC and an uplink PCC, and the remaining component carriers are referred to as Secondary Component Carriers (SCCs).
In the LTE system, transmission of a Physical Uplink Control Channel (PUCCH) on only one component carrier (i.e., the UL PCC) is supported at present, and the transmit power of PUCCH in each subframe is determined in the equation of:
            P      PUCCH        ⁡          (      i      )        =      min    ⁢                  {                                                                                                  P                                          CMAX                      ,                      c                                                        ⁡                                      (                    i                    )                                                  ,                                                                                                          P                                      0                    ⁢                                          _                      ⁢                      PUCCH                                                                      +                                  PL                  c                                +                                  h                  ⁡                                      (                                                                  n                        CQI                                            ,                                              n                        HARQ                                            ,                                              n                        SR                                                              )                                                  +                                                      Δ                                          F                      ⁢                      _                      ⁢                      PUCCH                                                        ⁡                                      (                    F                    )                                                  +                                                      Δ                    TxD                                    ⁡                                      (                                          F                      ′                                        )                                                  +                                  g                  ⁡                                      (                    i                    )                                                                                      }            ⁡              [        dBm        ]            
Where PCMAX,c(i) represents the maximum transmit power corresponding to each carrier,
ΔF_PUCCH(F) represents a power offset varying with different PUCCH formats relative to the PUCCH format 1a, configured by higher layer signaling;
ΔTxD(F′) represents a power offset, configured by higher-layer signaling, corresponding to transmission via two antenna ports; and when the PUCCH is transmitted via only a single antenna port. ΔTxD(F′)=0;
h(nCQI,nHARQ,nSR) represents a power offset, related to carried bits, calculated in a predefined equation varying with different PUCCH formats, where nCQI represents the number of carried periodical Channel State Information (CSI) bits, nSR represents the number of carried Scheduling Request (SR) bits, and nHARQ represents the number of carried ACK/NACK bits;
PO_PUCCH represents the sum of a cell-specific parameter PO_NOMINAL_PUCCH and a UE-specific parameter PO_UE_PUCCH, configured by higher-layer signaling, and this parameter is currently configured only for the PCC; and
      g    ⁡          (      i      )        =            g      ⁡              (                  i          -          1                )              +                  ∑                  m          =          0                          M          -          1                    ⁢                          ⁢                        δ          PUCCH                ⁡                  (                      i            -                          k              m                                )                    represents a Transmit Power Control (TPC) command cumulative value, that is, power adjustment values indicated in TPC commands received via a plurality of Physical Downlink Control Channels (PDCCHs) corresponding to the PCC are cumulated together as a power control adjustment of the current transmission, where g(i−1) represents a TPC command cumulative value of a preceding uplink subframe, and when PO_UE_PUCCH is reconfigured by higher-layer signaling, the cumulative value is reset as g(0)=0, and when a random access response corresponding to the PCC is received, the cumulative value is reset as g(0)=ΔPrampup+δmsg2, where δmsg2 represents a TPC indicated in the random access response, ΔPrampup is provided by higher-layer and represents a total power ramp-up from the first to the last preamble transmitted on the PCC; and δPUCCH represents the power adjustment value indicated by the TPC command obtained by the UE in the PDCCH in the correspondence relationships as depicted in Table 1 and Table 2, and can be obtained in the following two categories of PDCCHs:
In a first category of PDCCH, the power adjustment value is obtained from a TPC field in a PDCCH/Enhanced PDCCH (EPDCCH), corresponding to the PCC, with the Downlink Control Information (DCI) format 1A/1B/1D/1/2A/2/2B/2C/2D and scrambled by a Cell-Radio Network Temporary Identifier (C-RNTI) or a Semi-Persistent Scheduling C-RNTI (SPS C-RNTI); and if the PDCCH is validated as SPS activation or SPS release, then δPUCCH=0 dB; and
In a second category of PDCCH, the power adjustment value is obtained from a PDCCH/EPDCCH, transmitted in a Common Search Space (CSS) of the PCC, with the DCI format 3/3A and scrambled by a TPC-PUCCH-RNTI. This scheme relates to a TPC multicast scheme in which TPC commands for a plurality of UEs can be transmitted in the same DCI format 3/3A, and each of the UEs obtains its corresponding TPC command from the DCI format 3/3A according to a TPC-index preconfigured by a higher layer.
TABLE 1The correspondence relationship between the TPC commandfield in the DCI format 1A/1B/1D/1/2A/2/2B/2C/2D/2/3 and thevalue of δPUCCH indicated by the TPC commandTPC Command Field in DCI formatδPUCCH1A/1B/1D/1/2A/2B/2C/2D/2/3[dB]0−1102133
TABLE 2The correspondence relationship between the TPCcommand field in the DCI format 3A and the value ofδPUCCH indicated by the TPC commandTPC Command Field in DCI formatδPUCCH3A[dB]0−111
When the UE detects both of the categories of PDCCHs above in a subframe, the UE adjusts the power according to the TPC command in the first category of PDCCH, and if there is no PDCCH detected, then δPUCCH=0 dB.
M represents the number of downlink subframes for which TPC commands are cumulated, i.e., the number of downlink subframes, on the PCC, for which ACK/NACK is fed back, corresponding to the current uplink subframe, and km represents an index of each of the M downlink subframes, where M=1 and k0=4 for Frequency Division Duplex (FDD), and M and km are dependent upon the TDD uplink/downlink configuration for Time Division Duplex (TDD) as depicted in Table 3 where M represents the number of elements in the set K.
TABLE 3The set K of indexes of TDD downlink subframes: {k0, k1, A kM−1}Uplink/downlinkSubframe indexconfiguration01234567890——6—4——6—41——7, 64———7, 64—2——8, 7, 4, 6————8, 7, 4, 6——3——7, 6, 116, 55, 4—————4——12, 8, 7, 116, 5, 4, 7——————5——13, 12, 9, 8, 7,———————5, 4, 11, 66——775——77—
Noted here the plurality of radio frames are arranged in sequence, that is, if the last subframe in the radio frame a is represented as k, then the first subframe in the radio frame a+1 is represented as k+1, and Table 3 illustrates K corresponding to the respective uplink subframes merely taking a radio frame as an example, where n−k<0 represents a downlink subframe in the preceding radio frame.
Particularly if the UE does not transmit PUCCH, but receives the DCI format 3/3A in which a TPC command is carried, on the PCC, then the UE determines PPUCCH(i)=min{PCMAX,c(i),P0_PUCCH+PLc+g(i)} [dBm].
As illustrated in FIG. 3A, FIG. 3B and FIG. 3C, the LTE system supports three duplex modes of FDD, Half-FDD (H-FDD) and TDD.
TDD-FDD Carrier aggregation may be supported in the evolved system subsequent to the LTE-A system. Since the FDD carrier and the TDD carrier operate in different modes, a new uplink Acknowledgement/Non-Acknowledgement (ACK/NACK) transmission solution may be introduced, that is:
The eNB groups the aggregated downlink carriers into N sets as Si of downlink carriers, where a downlink carrier belongs to only one set of downlink carriers. The carriers in the same set of downlink carriers operate in the same duplex mode. The same TDD uplink/downlink configuration is applied to all the TDD carriers in a set of carriers.
The eNB configures the set Si of downlink carriers with an uplink carrier CUL,i, where the same duplex mode as the set of downlink carriers is applied to the uplink carrier CUL,i and the same TDD uplink/downlink configuration as the set of downlink carriers is applied to the uplink carrier CUL,i. Uplink carriers corresponding to different sets of downlink carriers are different from each other as illustrated in FIG. 4.
The UE transmits ACK/NACK information, corresponding to downlink data received on the downlink carriers among the set Si, via a PUCCH on the uplink carrier CUL,i, that is, the UE can transmit PUCCHs respectively on a plurality of uplink carriers.
Apparently if ACK/NACK feedbacks are transmitted per set of carriers, that is, aggregated carriers are grouped into a plurality of sets of carriers, and an uplink carrier is specified for each set of carriers to feed back ACK/NACK of downlink data received on the carriers in the each set, so that the UE may be configured with a plurality of uplink carriers to transmit PUCCHs. There has been absent a corresponding solution to controlling PUCCH power when the UE supports transmission of PUCCHs on different uplink carriers corresponding to different sets of carriers.